In general, there is known a vehicle guiding method to prevent a lateral surface of a vehicle body from coming into contact with an obstacle in the backward direction of the vehicle when the vehicle moves backward. This method guides a vehicle by superimposing, on the monitor, a pair of left and right predicted-trajectories corresponding to the vehicle width in accordance with a steering turning angle (see Patent Literature (hereinafter, referred to as “PTL”) 1, for example). Moreover, another known vehicle guiding method is to guide a vehicle through the current state of the vehicle by superimposing, on the monitor, fixed trajectories corresponding to a zero steering turning angle (see PTL 2, for example).
Furthermore, there is known a vehicle guiding method used when the driving support target is a tow vehicle in order for the tow vehicle to be coupled to a tow-target vehicle. In general, when a tow vehicle is coupled to a tow-target vehicle, the tow vehicle is moved backward so as to move a tow vehicle side coupler (e.g., hitch ball) installed at a rear portion of the tow vehicle to the vicinity of a tow-target vehicle side coupler (e.g., towing hitch). For moving the tow vehicle side coupler backward, there is known a method that accurately guides a vehicle to perform positioning between the tow vehicle side coupler and the tow-target vehicle side coupler, by superimposing, on the monitor screen, guiding lines for positioning between the tow vehicle side coupler and the tow-target vehicle side coupler (see PTL 3, for example).